Practical considerations in the deployment of ground source heat pumps in older properties - a case study

A ground-sourced heat pump (GSHP) was installed in a former Vicarage in Cambridgeshire, with a mix of solid wall structure built in the late 1800s and cavity wall section built in the 2000s, previously heated by oil. This type of building is usually considered unsuitable for heat pumps, unless substantial insulation work and extensive replacement of radiators are undertaken. Although the building had undergone a degree of retrofit to increase insulation, the GSHP was installed with the existing radiators. A detailed thermal model for the house was built in ESP-r and validated against experimental measurements taken from sensors in every room. The expected heating demands were computed from the model based on weather data and the GSHP system was designed accordingly. A compromise was made between minimizing the size of the heat pump and the achievable energy savings, which could have important implications for the way incentives for low-emissions heating systems are set up. Using the initial SAP assessment would have led to a substantial oversizing of the heat pump. The data collected so far show that an SPF of 2.9 has been achieved whilst maintaining comfortable (18 °C) internal temperatures and emissions of CO2 have been reduced by 70%